The invention relates to function generators, in general, and more specifically to the determination of the coil diameter and speed reference signals in a reel motor drive system.
It is important for the operator to be able to controllably accelerate, or decelerate, a reel motor drive system from some initial speed to a selected terminal speed. This is particularly useful in a rolling mill, in a paper mill winder, where a strip of material is being unwound from a pay-off reel and rewound on a delivery reel. The tension of the strip is to be maintained constant as a function of varying diameters on the reel, and the motor drives are automatically controlled in speed for that purpose. Accordingly, the rate of change of the speed, depending upon the size of the reels and the nature of the strip, has to be defined and set under varying circumstances by the operator. Moreover, in a rolling mill, where the strip is passed through processing roll stands, the stands are controlled in speed under a master reference with individual stand speed regulators maintaining constant mass flow between the pay-off reel and the delivery reel. In such a case, it is necessary to be able to adjust immediately the speed rate collectively and individually at each stand as the overall process requires. In particular, when changing reels between pay-off and delivery ends it is required to stop winding at the operator's command and to rewind, or unwind. All these operations require the knowledge of the coil diameter since it initially determines the calibration conditions, and when running it conditions tension adjustments and inertia compensation for acceleration and/or deceleration.
It is common at the present time to instantaneously calculate the coil diameter and calibrate initial and final coil diameter values with operational amplifier circuitry. However, operational amplifiers are subject to drift.
It is now proposed, for coil diameter calculation and calibration, to take advantage of digital treatment and microprocessor technology in order to improve both cost and sophistication and at the same time provide an equipment which can be handled by an operator devoid of the expertise normally required in programming and customizing the equipment in the field.